The laws of Boneh/Soser on Yom Tov slightly differ from Shabbos; at times it retains the Shabbos restrictions while at others it is permitted to be done. The following is the general rule: All items that are Biblically forbidden to be built or destroyed on Shabbos are likewise Biblically[1] forbidden to be built or destroyed on Yom Tov. However those items that are only Rabbinically forbidden to be attached or detached on Shabbos, at times is permitted to be done on Yom Tov.

Attaching parts of vessel lightly together:[2] It is permitted on Yom Tov to loosely attach parts of a vessel together, even if it is commonly inserted strongly. It is forbidden to insert it strongly. One may thus loosely insert the leg of a table or chair, [and the handle or lens of glasses[3]]. [If however the vessel is large enough to hold 40 Seah, or is attached to the ground, it may not have its parts attached even lightly.[4]]

Opening an envelope:[5] One may tear open an envelope on Yom Tov. [According to those who hold that opening cans on Shabbos is forbidden due to Tikkun Keli, it is to be opened in a destructive manner, just as they rule by cans.[6] However according to those who hold that cans may be opened in a non-destructive manner then seemingly it is permitted to open an envelope even in the area of the glue, by separating the two parts.[7]]  

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[1] Admur 519:6

[2] Admur 519:5

[3] Piskeiy Teshuvos 519:1

[4] Piskeiy Teshuvos ibid

[5] Admur 519:6

[6] See Piskeiy Teshuvos ibid; Bris Olam Koreia 7; based on Chazon Ish 61:2; SSH”K 28 footnote 14-15

[7] Ketzos Hashulchan ibid

The reason: Although on the onset it seems that doing so should be forbidden due to Koreia, as it is forbidden to separate glued items, as written in 340:17, nevertheless in truth one can argue that in this case it is permitted to do so as a) the prohibition only applies by two entities that are glued together as opposed to a single entity, and b) It was sealed with intent to be opened, and is hence a temporary sealing. [Ketzos Hashulchan ibid]